Cable systems use coaxial cable and multiple connectors and housings to distribute television and data service signals across large areas. Electromagnetic shielding is important to prevent the signal from leaking and disrupting over-the-air legitimate signal (specially aeronautical transmission). Consequently, signal leakage detection assessment, generally compiled into a Cumulative Leakage Index (CLI), is required to meet FCC (Federal Communication Commission) regulations of the United States, or the like commission, as well as for preventive maintenance.
The leakage detection can be done in different ways, using a specially designed receiver with either a dipole antenna at half wavelength (as per regulation) or a short monopole antenna. The latter, commonly called a “rubber ducky”, is rugged but not matched to the receiver, less sensitive and has no directivity. Leakage detection is usually performed using specific installations, and also can be performed by so-called patrols across large areas, either on ground or on an aircraft.
Cable signals, especially when other signals could be found to be of close frequencies, are usually “tagged” with either amplitude (AM) or frequency (FM) modulation for identification purpose, helpful during leakage detection assessment.
Presently, there are two (2) types of measure instruments for leakage detection: a self-contained leakage detector or a leakage detector combined with a SLM (Signal Level Meter), a common instrument used and carried by cable installation personnel.
Thus, there is a need for an improved leakage detection apparatus.